American Thoracic SocietyJEu ropean Respi iatory Society

Respiratory Function Measurements in infants: Symbols, Abbreviations, and Units

CONTENTS

Introduction International System of Units Symbols

Symbols for quantities Symbols for units Practical amendments Special notations and mathematical operations Conversion of units .

Abbreviations

OFFICIAL STATEMENT OF THE AMERICAN THORACIC S O C I ~ AND THE EUROPEAN RESPIRATORY S D C I ~ WAS ADOPTED BY THE ATS BOARD OF DlRECTQRS (NOVEMBER 1 m) AND THE ERS EXECUTIVE COMMITTEE (SEPTEMBER 1994).

Cornrnunimtion about infant lung function tesking, as in any other field .of science and medicine, rquires the use of symbols, ab brwiations, units, prefixes. and suffixes. These should be unam- biguous, and this is achieved by rigororrs standardization by in- ternational scientkfic and medical W i e s and governments. The present recommendations derive from the report of the European Comrnunityfor Steel and Coal and the European Respiratory Se ciety (1). However, the list of abbreviations has been modified and extended by the joint ATSERS Working Group on Infant Pulmo- nary Function Testing to be appropriate for the Field of infant lung function testing.

INTERNAflONAL X X E M OF UNITS The International System of Units (S1 units), which has superseded previous systems of units, offers the great advantage that it is a caherem system. Hence, any relationship between units based on products and quotients of physical quantities does not require scaling factors.

Measurements are described in terms of a quantity. Quanti- ties are characterized by their name, a symbol for the name, a name for the asociated unit, and a symbol for that unit. Thus, for body weight the SI quantity is mas, symbol m, unft name and symbd kilogram and kg, respixtively. A f&h quality is dimension, which does not have bearing on the present text and is therefore not discussed.

S1 base units pertinent to infanl lung function testing are listed in Table 1. Other units derive from these; a selection relevant to respiratory physiology is listed in Table 2. For practical purposes,

This Stdtement was developed by Phillp Quanjer, Janet Stocks, and Peter Sly in conjunction with the ATSIER5 Working Group on the Standardization of lnfsnt Pulmonary Function Tern.

T h i s paper is being copublish& and copyrighted with the Eurapern, Respim- tory /oumI* Am Rerpk Crit Carr Mcd Vol 151, pp 2047 -2057, 1 W5

some non-St units that are widely applied in everyday life have been retained for general use wRh the $ 1 ; relwant ones are listed in Table 3.

The S1 base units give rise to the unit for volume being m3, that for flow m3.s-: and for pressure h. The former two units are cumbersome in daily practice, as both lung volumes and ventila- tory flows are only small fractions of the units given; conversely, the pascal is only a small fraction of pressures normally encoun- tered. On that account, the liter and the kilopascal have been adopted as basic units in respiratory physiology. Furthermore, in respiratory physioIogy and medicine, the SI base units are ex- tended with SI derived units (Table 2) and SI prefixes (Table 4).

SYMBOLS

Symbls for Quantities

Symbols are used to designate specific quanfties, including ba- sic quantities (e.g., volume, time, pressure, amount of chemicak substance) and derived quantities (e-g., vorume by unit time or flow). Letters from the M i n or Greekalphabet are commonly em- ploy& as symbols, either roman type as in the United States or italics as recommended by the European Respiratory Society and the European Community for Steel and Coal El). As the number of letters available is limited, inevitably one symbol may be used to designate more than one quantity (e.g., Celsius temperature and time are both denoted by 2)-

Symbols for quantities may be s-ed by one or more sub scripts andlor prescripts (abbreviations) andlor modifying signs (dashes, dots, primes), for example AV. Subscripts other than numbers are printed in roman smdl capitals or lower case let- ters. The order of specification is lowtian (where), time (when), condition, or quality (what, how). Specifications are printed either in line with the primary symbol, when they are preferably printed in smaller frrnr size, or as subscripts. When more than one sub- script is used, these are separated by a comma. Examples in- clude PL,Zi,vis (PLtid] for pressure in the lung (where) to wer- come tissue viscous (what) resistance; and Fsp,l, He (Fml.Hs) for ftactjonal concentration of helium (what) measum in the spirom- eter (where) at time 1. Further examples of the natation of eorn- rnonfy used indices are given in Table 5.

Symbols for Unitr

Symbds for S1 and non-SI units are m a n lower case letters (e.g., m b r meter), unless the name ofthe unit is der iw from a proper name, in which case it consists of a capital roman letter (e.g., K for kelvin). or a capital m a n and a lower case letter (e.g., Pa for pascal); the exception is ohm (a). Prefixes are used to rnodii synt

h k for units and are single roman capitals or lower case le t te~ (except d m , da). Selected Sf prefixes are listed in Table 4.

Practicaf Amendments

It is mmmended that time be reparted in secands for quamas that relate to instantaneous events: tirnsaveraged quantities should be reported in units that are appropriate to the length ot

AMERICAN jOURNAL OF RESPIRATORY AND CRmCAL C4RE MEDICINE VOL 151 1995

TABLE f

SF BASE UNrrS

Name of Symbl for NameafQuanMll ~ n a Unit

m Mass k i b m kS Tine second S

Themdynamic tmpature kehn K Amount of subtance mole mol

TABLE 2

Name d m Definkn N m of OuantRy Unit for Unit ot Unit

Frequency her& H x sl F o e nemton N m -W+ Pvesw re W a Pa N-mz f nergy, wwk joule J N-m P m r wall W J-st Celsius temperature degre% "c

Celsius Dynamic -4 pose P l Ws.Pa-s Kinematk viscosity stokes St 1 P.rn2s'

- ~ ( f ) i s M i n w l s l h e G r f f e n m f a t - T - T,berweenme-b tempfa- 1 and ?, = m.15 kelvin.

TABLE 3

Name of symbol Deffniblon Name of OwrdiIy Unfl for Unit of Una

l7me min- min 60 a M u r h 3 8 W s day d 8bt00s y%ar a 365 d

V O l W hter h 1 r = n+ 81& presstoe rn~lrrmeter m M 1 3 3 m pa

ot menury

time over which they are obtaiwd (q., seconds, minutes, hours). For special purposes, the units day (day). month (m). and year (a) may be used.

Volume of gas is usually e x p ~ ~ ~ d in h. NOfe that in this case the subscript refers to the unit. In a previous recommenda- tion (I) the symbol for liter when not assaciated with prefixes was printed in italics bemuse the distinction b W n 1 (one) and 1 (for Irter) with most fonts was often too subtle. The wrking group considers that the capital L is more practical; thus, the m i o n is L for l i r and rnL for milliliter. Note that the basic unit is the liter, butthat for infant lung function testing it is sometimes practi- cal to e x p m results in milliliter. Similarly, while the basic unit for the amount of gas is the mole, it is more practical to express resub in rnmol. In the same vein, the unit of length is the meter, but obviously, q.. crormheel length may be reported as cm. In the case of resistance, it is metical to adhere to the set of coher- ent basic units. Thus, when expressing volume in L, flow in L-s-l, one avoids curn'bersom Slgures when converting to mnductance, specific conductance, and specific resistance.

For the partial or total pressure of gas, the basic unit in respi- ratory physiology is k h ; howem, for blood pressure mrn Hg is temporarily permitted.

Special Notations and Mathematical Operations X mean value of X X' time derivative of X (eg., V' for i-us flow)

i P - M 1 6 kilo It 101 hedo h i 0' c k a da 1W' deci d 1 r z -ti c 1 ITa mil11 m 1F micro P

10- nano n

TABLE 5

MAMPLES OF NOTATlONS OF COMMONLY USED INDICES OF PULMONARY FUNCTION

m- CL ow; EXs; a.*: Crs.~: &.MOT

R e s i Raw; & drs: F ) a w , ~ &,I; Rrs.im

Lung vol- F ~ C p r n ; FRCne; FRCN,

Volumes and Ocmrs Vr: V & . m : v: m F R C

Pr-re PA; A; PdO; P4C01; Rc.4; %ti,* P(~rn),%

Tming n;teE:not:m

X" second time derivative d X (e.g., v" for volume acceleration)

x' timemetaged value of X'(unZts of time to be specified) (e.g., PE in L.rninq for minute ventilation)

AX4 chawe of X for specification A, @.a. XA-E

XA,B %X X%Y m x-Y X-Y'P x-m (x-w-'

difference b e h v ~ e i ~ X-values for &-!icationi~ and 8 e.g., P(A-a),% different speckhations of X are sepamted by a m m a X as a percentage of the reference ~ 1 u e X as a percentage of Y division is indicated by a solidus (stroke) multiplication is indicated by a raised dot

exampfes of mathematical notations

The working group reGommends X' for the instantaneous time d e W i and For the avwaged time derhmtk because t h m can t>e easily handled byword processors. For the same reason, the second time deW+be of X is indi- by X". Where it is typographically impractical to indicate that one is dealing with an averagd time derivative, X' is permitted.

The notation WY is aim, except with complex notations. Morethanonesolidus~uld never be E& inanotationbeGam it is ambiguous. For emmple, AlSJC can be interpret4 eaher as A-B-3.C-S, when il had better been written as: M(BC) or AC-B-', when it would have been urnambiguous whenwntten asAI(B1C).

Camerrion of Units

Table 6 lists some eornmonfy used traditional and SI units and conversion factors to transform from the traditional m the new units.

A T S / W Statement

TABLE 6

COWRSION FACTORS

Quantity

Compliance Conductance Elastanm Gas cwlcermatbn' Gas flow- Pressure

Trildiional Unit

1 L-cm H,W t t .r1.cmHp5 1 cmH,O-l;' 1 rnL.100 ml-' f rnkm~n*~ 1 m&O I mmtlg 1 unH,O~L"+s 1 mt.m~n-'mmflv 1 rnL.403 ml-' I a h 1 0 0 mL-'

' Tip Mlums of 1 rwie at SfPD W . P l&r. Thus, an w n CDlnnpbbo 81 20 mL-m-' ccrrres M 0.9 rnm0l.mm-', an oxygm cMmnbatim of 2096 lo 9 -L'.

Abbreviations are employed to facilitate written and spoken corn rnunication and are commonly specific to individual languages. Howwer, there is atendenw for many abbreviations to Ix adopted worldwide; they are also used in maffiematical formulas and equa- tions. Such abbreviations haw acquired the atbibures of syrnbals, Commonly accepted standard abbreviations for quanfities are usu- alty written in one or more capital letters (thus, lung capacities and their subdivisions are denoted by TLC, RV, FRC, etc.), but there are many exceptions (e.g., H b, CAMP, coA, ATPase). The abbreviations can be specified hy one or more subscripts and/or modifying signs (dashes, dots, primes). Subscripts are nurnkrs or letters printed in roman small capital ar small lower case type, e.g., FEV,.

The following Wes contain abbrwiahm symbols, and units for commonly used lung function i n d i Gas volumes are at unless otherwise indicated. Qualifying abbreviations are usually one or more roman tower case letters. Hawever, for several qualfi cations, capital letters are (also) accepted.

The synb l for time is t, hence the d i g gmup wishes tQ discourage the use of Te, T, E, TI and recommemds the use of tE and fi instead.

Flowdescribs the rate dchangedvolume (volwmerate), and flow me is therefore equivalent to volume acceleration. Hence, flow rather than flaw rate should be used to denote the rate of change of volume.

Functional residual capacity (FK) is by definition the mlume of gas remaining in the lung at end expiration, irrespective of the determinants of the FRC. In healthy adults and normal children, the FRC at rest usually coincides with the elastic equilibrium vol- ume (EEV), i.e, the Yolume at which the o W r d recoil of chest wall bakances the ima-d recoil of the lungs, so that net m i l pres- sure is zem This is confusingly ref- to as 'passive !%C." In infants and those with lung disease, the lung volume at end expi-

ration may be maintained abwe El% and this is often r6femd to as 'dynamic FRCam The correct term for end expiratory volume in either circumstance is FRC.

3rhe thoracic gas volume is the volume af gas in the thm at any point in time and any level of a~ larpressure. It is usuajly measured by whole body plethysmography; in patients with o b structfve lung disease it may give appreciably higher results than gas dilution methods. Therefore, lung volumes thus assessed are commonly denoted by TGV. As TGV may be determined at any lwei of lung inflation, the level should be specified. Thus, E V is too unspecific, and it is suggested that its use be abandoned, but that the measurement method is denoted in a subscript. Thus, the FRC measured by whole M y plethysrnography, helium, or nitrogen dilution is denoted as FRCpleth, FRCH~, and FRCN,, respeztkety. This appltes similarly to other lung volumes.

Specific compliance is frequently used in adult resphatory pa!hophysiology, when it is the ratioof static lung oompliance and Fung volume. In fact, the term volurnic cornptiance would be more appropriate. Specific compliance is also frequently used in net+

natal work. Here, h m r . it is frequently not possible to mea- sure lung volume. Since lung volume and body weight are linearty related, in neonatal work lung mrnp!iance is commonly site cor- rected try taking the ratio of comphance and body weight. As it is misleading to use the term specific compliance for both ratios, it is recommended that use of the term should be avoided, and CLNL or C L M for mrnpriance per unit of lung volume and body weight, respectively, should be reported instead.

MEFxOh and FEFx% merit special mention. MEF is the maxi- mal flow obtained during an FVC maneuver delivered with maxi- mal -when Row is effort independent. Some argue that larger flows can be attained if the maneuver does not entail maximal Mort, so that it would be mare appropriate to speak of forced ex- piratory flow (FEF) ratherthan maximal expiratory flow. This tends to obscure the specia! relationship b e t w e n the maximum Row and the maximal effort. Also, R should be noted that MEF is d+ tennined when x?! of lung volume remains to be exhaled, while FEF is determined when x% of lung volume has been exhaled. Thus, FEF,, = MEF-; the two are complementary. This eas- ily Leads to conhion. Finally, V- is widely used and corm sponds to MEF- ratfrer than FEF- Hence, the use of MEFXpb is recommended (1).

~~E The Wmking Grwp ac-ge permperm- trwn the ECSGERS Working h!ly ln use ancl expnd the ?Mement they preparsd, and are g-l to R. Cutma, M. Gappa, S. Go-. S. Kanq A. C, mum bourlls.T. N~m+ai.J.M.e)eA. Lopez. J.H. Paiva&Carvalho,S P8dersen, and H. S d 4 fm -lation of terms and defin+tions. The financial support by G l m Austral& Gbxo Group Research Ud UK. and Glpro Sweden AB is also pMful ly achrmledged.

1. Quanjer, Ph. H.. 6. S. Jarnmellm. .I. E. Cotes, et af. 11993. SymMs, ab breviations and units. Report working Patty uf European ~Gmrnunny for Steel and Coa): Ofticia1 Statement ot Eu-n Respiratory Society.

EI-

alv#rlair Iesftijd: jaur o p m i l k : aficrjet

absoluut anatomisch

lwh-%npmiag

s o d

paraded -* pevion baromB niqrre am-

-& presSirm bammt- tiqw mbiantes, d'=gaz= -a @on bammt- eiqut ambian- re% du E= m vap l r d'ta€l dam ccs &rims wits atnenncs

omgevingstempe- namrrabaromt- ~~m v d g d met waterdamp bij die -dl- luchrwcg

-dl?: kg (SAX a d l w)

index:

-&tic lab=: W.*' brwEhial body s* M y s d a c e - KG

-tempcramre,

pnmmadsatu- raredwhmwater

v a ~ o o r e - Ewditiars

Gnmdumsafz: kf.rnin-1 bronchial K h p m b d k k K-: n? Kikper-T-. B - d 1m wi-J =a'Jw

k s a l n E t a b h: Uamin-1 bmIKhd hchimqpmlak h-k i+

he- tuur m dnk rer- a g d met wam- damp bij deze om- -- volumi& (speci- &kc) cmplianrit van 6 long k h - 1

m h c compliantie van $e bug: L-kh-1 mmreftjm

~ C L T ~ LR1 hmdehi Lkmirr' (fie m k p?

ArSlERS Statement

Pesaiption - QmuriQ - Unit

a~vmkit 1 H Uder & Ska (2) yla: rnl : rn: anericlE 33M absolut #&H anatomipk MSl3Et Iu%€m@ng 5 S R B

tern- y m i 6 1 1 b a r b m a arnbimtalcs "nperatunyprrsi6n barbmenica ambientales. sio hum& tcrnpcratara y prtssib ambientales con satumtdn de vapor & agua em cstas cnndiciom

via peree via &ma

rrma wrpoml: kg ( v a tambih indice & massa c o w : m a w ~ c s l a ~ l f a ~

~ G a

po.-cmpak kg twr ~~- W) indim de masg

cmpd: mass a ~ -

taxa matab6Iica basal: H.min-J bronquial superficie dd cuerpo akca ao@: ~

h p p e w = w s x p s 0 ~ lufmykochma- tad mtdl wmnhga UnderdcaPa Mngclscr

m p - dislmsi- &brT(oor: L.kPa-t compliawer L-19a.j 3 >73 4 7 > X : bilidadt: Lkh-1 LkW c o m p ~ - T m &mj E v h K b r y w ~IynweIattrad I%s@1 do plmZw kPa-1 T O W ~ ~ + L W C L ~ ~ (sp5fk)ltmg- f iz>y?d?>x:

tov 6yEo: LPal compl- 1;Pa-I kPa4j complaczncia W C a E W ~ L I J I ' E V ~ ~ dyiramisk lung- @ms3 do p u e Lm' .cm,- mrnpliaaft 9774723

2046 AMERICAN jOURNAL OF RESPIRATORY AND CRITIfXP CARE MEDICINE W L 1st 1995

dbh&&~n Symbol

C

AEEL diff- bctartta EEL. and EEV: L

EEV cLasric qihbrium rofum: I

FEVt ~ C X ~

VdPIIk iP t scwnds:L

FEVK%VC F E Y t s a m ~ ~ f f h c v i t a l W t y (W be specified)

k fictiod. flow icsistive

FRC ~d~ capaciry: L ~~ ofamtasurememm

kspeFifiad) FVcrrm flow-volamc awc

g e t

t.r'.kkrL 6dK {SG") * (*)

airway

h Z k k I

lv P-=

W e r e r p i r a - minx Ink'. s" (wyez mi RR) &it u p h i o i ~ maximal* L r '

Volumen am elasti- scben Equilibrium: L ehlizcb - p k d

volvnac bij d a s k h mwicbc L

&&mde~wan- 6atie win ahtan- tic i

q d e : mirl.

(= a w gef- mid- ~~ L.s~

M o d e mi- kt L (spcdficta bepa- -1 skmm-volume CPrVE

gef- expira- toirt vitalr GI@-

ac L

e- m-L-I c k s p t m m slut txpmbmk aiw: L fm%kcl d m EELogEEV: L

foma- r i s k w h i t -- L FEVt aa@W i p =t af VC (qm5- -1

ATS/ER5 Statement

Swedish Jw-=

lwdSfr6m mi d- a m

tIasrafida: m.L-1 espiratmio nivel de final dt cspiraci6n: L dif& en* EEL y W : L volumm dc @ i elastic: L

k-@m av kompnemm i ~~: w m : mid. s' m'. 5 . 3

(se h e n RR) format mittexpi- m m m n w ~ s '

~~: miu'. s'

(w-w fluxo +ria f a e a t r t o s w 2 5 e 7 5 dactwadccapaddade vital fmp& L-ri w l w txpirst6no for- Tgdo em t segandos: I.

vitale forrata: Lasl volumctspirawrio v o l u e n ~ d w p a e in r d f- en r segundw: L L FEVr~spr r s~o in F F V t ~ m m 0 b-c deUa pmmtaje ck la la- capwa rifale dad vilal (&be espifi-

FEvt -gem da mpddzwk vital (a

-1

2048 AMERICAN IOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE VOL 151 1995

Tngbd @- tam): kPa-L-=4 u-

imma&

bt it iv.

lmK&

&.*i.L-l

(see &a m)

m ==kg nmdaiml

I d s - -=

minimal

ATS/ERS Statement

~Gbreviatim M p t i o n - Qmntlty - Uait Symbol

Idiano w h g u i s EnqvlKcf Swedish Japanese

alrr;zza in picdi tab en pwici6n de pit allma (em p6). SW ( m ~ WVJed 3f:m (mtma): m (vdue (tstarura): m (ver rn ( v u 6-): @ME (&ndt): rn anchc L) tambih L) mnbsm L) m-otl5 L) (se Svtn L) rifltsso di reflqo de in&lcik rcfltxo de M a q k de m w a h m 5 Hering-Bmm H ~ T & - B ~ ~ E # Hering-Brews de Hering-Brwcr Hering-Brew St- Hesing-B- jnflati-flex

E r n Jim lunghtnaI- 1-m tall-): m PO- - I d e Meid

laminar

lim '19 blt h g d lhjkz-M): S S : m rn

tuega FF lateral film lami& W ( f a 3

b* -; peso: b r m a n b w&pcivtl ~ - M s ) v i a ( s I m* m s ) : kPa ~ c r l r a p k r

flusso espkwio MEF araadrr el x% de mdiosdundetmni- hWCaim&hwr mra livcllo ptnwmu- wpirada: LR' (w ale di vitalc tambi& V m ) f m a m aa tspirme: L-r' /w&e artche V s a ) eurva flusw volume rn dt flup vdumen

w- -- eurva d&ibwlum expint&ia maxima

minimal Sd\

2050 AMERICAN JOURNAL OF RESPIRRTORY AND CRmC4L CARE MEDICINE KOL 151 1995

Ab&wiation Symbol

w

p-wiw wn- ccnoa&on of h u - chocoamicaa- sing FEV, la0 fall x% frnmbasdinc: mg.L-1. mtml..L"

k - "on af bronkok-, dmkvirkeraw m, pa x% af

k h o - rim SabsEaDz die &m~ x s i g m Abfd aes FEV] v m m d x mg-L-I, d . L - b

dostdagwtZaop

pfivoqaam- ChttckvEMSde x 8 de la valcur base: m g pmol pressionpwhfdt finbtxpiratimrn e b i t cxphom

dosis. ds kv i r lm et fald i FEV, x% af lxigangs- w d k m mg,

w l

PIP p i c e - . . mplm%mkPa P- PI- - W e

d 0.1 5 a@ l ' o a l ~ des v a i a

d'txpiratioa:kPa pieion hictiop nelk & tisru pulmonaire: k h

U r k frimkdpresna in the ftmg tissue: m